| Type: | integer |
| Default: | 128 (1MB) |
| Min: | 0 (0kB) |
| Max: | 2147483647 (17179869176kB) |
| Unit: | 8kB |
| Context: | sighup |
| Restart: | false |
| Since: | 9.6 |
Specifies how often the WAL writer flushes WAL, in volume terms. If the last flush happened less than wal_writer_delay ago and less than wal_writer_flush_after worth of WAL has been produced since, then WAL is only written to the operating system, not flushed to disk. If wal_writer_flush_after is set to 0 then WAL data is always flushed immediately. If this value is specified without units, it is taken as WAL blocks, that is XLOG_BLCKSZ bytes, typically 8kB. The default is 1MB. This parameter can only be set in the postgresql.conf file or on the server command line.